Electric discharge lamp system and method of operation



H. K. BOURNE 2,469,357 ELECTRIC DISCHARGE LAMP SYSTEM AND METHOD OFQPERATION Filed om. 1946 May 10, 1949.

A. C. SUPPLY CIRCUIT INVENTOR: HARRY KEBBELL BOURNE,

HIS ATTORNEY Patented May 10, 1949 ELECTRIC DISCHARGE LAMP SYSTEM ANDMETHOD OF OPERATION Harry Kebbell Bourne, Rugby, England, assignor toGeneral Electric Company, a corporation of New York Application October8, 1946, Serial No. 701,966 In Great Britain December 27, 1939 Section1, Public Law 690, August 8, 1946 Patent expires December 27, 1959 3Claims.

My invention relates to electric discharge lamp systems and moreparticularly to systems and methods of operating electric dischargelamps intermittently or periodically.

I-Icretofore it has been suggested to produce intermittent flashes oflight by the utilization of an electric discharge device, or lamp of thehigh pressure metal vapor type, and periodically shortcircuitin animpedance in series with the lamp so that the power output isperiodically increased thereby causing the luminous output of the lampto rise and produce light flashes of large luminous output. The priorart arrangements have been deficient particularly with respect to thefact that no provision is made for assuring that the lamp ispre-conditioned to furnish the large luminous output when subjected toirregular or uneven time patterns such as that encountered in sendingflashes of light for signalling by code.

It an object of my invention to provide a new and improved system foroperating electric discharge lamps.

It is another object of my invention to provide new and improved methodsof operating electric discharge lamps intermittently.

It is a further object of my invention to provide new and improvedsystems for pro-conditioning and preheating electric discharge lampswhereby uniformity of light output at high levels may be obtained eventhough the lamp is subjected to irregular or uneven time patterns ofoperation.

Briefly stated, I provide a new and improved system for operatingelectric lamps, such as electric discharge lamps of the high pressuremetal vapor type, which require predetermined initial temperature andpressure conditions in order to produce a desired luminous output. Forexample, in electric discharge lamp systems intended for operation toproduce periodic or intermittent light flashes, it is desirable thatmeans be provided to assure adequate heating of the discharge lamps notonly initially but also during the intervals of time between the flasheseven though the flashes occur in irregular or uneven time patterns.Accordingly I provide, in a system for obtaining intermittent flashes oflight, means for intermittently or periodically shortcircuiting animpedance in series with the lamp to increase the power input to thelamp while maintaining the arc discharge in the lamp during thesimmering periods of reduced power input. More specifically, the systemis arranged to transnut to the lamp a predetermined minimum value ofsimmering current, which may be defined as a value of current suitablefor maintaining an arc 2 discharge therein. Provision is made toincrease the value of simmering current transmitted to the lamp to avalue greater than that existing during the periods of reduced powerinput and less than that existing during periods of increased powerinput, when the period of reduced power input is in excess of apredetermined time. In this manner, the lampis pre-oonditioned so thatthe lamp rapidly produces high level luminous output upon increase ofthe current supplied thereto. Where the lamps are of the filamentarytype, electrode or cathode heating means may also be employed to provideconstant heating current to the filamentary cathodes therebysupplementing the preheating and pro-conditioning effeet as describedhereinbefore.

For a better understanding of my invention reference may be had to thefollowing description taken in connection with the accompanying drawingand its scope will be pointed out in the appended claims. The singlefigure of the drawing illustrates an embodiment of my invention asapplied to a circuit for operating a lamp intermittently from analternating current supply circuit. 7

Referring now to the drawing, I there illustrate one embodiment of myinvention as applied to a system for intermittently or periodicallyoperating an electric discharge lamp 1 at relatively high levels ofluminous ouput. The lamp I is preferably of the high pressure metalvapor type, such as one employing mercury vapor, and may includeelectrodes 2 of the filamentary type which are supplied with apredetermined value of heating current through transforming means 3energized from a suitable source of current, such as an alternatingcurrent circuit.

In order to limit or control the current transmitted to the lamp I fromthe supply circuit I provide impedance means which may comprise a singlemulti-tapped reactance or which comprise serially connected reactors 4,5 and i2. This impedance means serves a plurality of functions one ofwhich is the establishment of a predetermined minimum value of simmeringcurrent to maintain an arc discharge within the lamp l during periods ofreduced power input. Another function is the transmission of increasedvalues of current to operate the lamp at high levels of luminous ouputupon short-circuiting of predetermined parts thereof by elementsdescribed hereinafter. A third function is thetransmission of a secondvalue of simmering current greater than that existing during the periodsof reduced power input and less than that existing during periods ofincreased or high power input.

As a means for increasing the current transmitted to lamp I in responseto a predetermined circuit controlling operation, I provide anelectroresponsive device or relay having an actuating coil and contacts6 which short-circuit reactors 5 and I2. Relay 1 may be initiated in itsoperation by an initiating means or key 8 which is connected in seriesrelation with the actuating coil of relay 1 across the supply circuit.Contacts 6 of relay 1 are normally open.

As an agency for modifying the action of the relay 1 when the intervalof time between succeeding periods of operation thereof exceeds apredetermined value I provide a time delay electro-responsive device orrelay 9 having an actuating coil and normally closed contacts I3 whichshort-circuit reactor I2. Relay 9 may be connected as shown to beresponsive to the voltage appearing across the actuating coil of relay Iwherein a unidirectional conducting device or rectifier I I is connectedin series relation with the actuating coil of relay 9. The time delayoperation of relay 9 is obtained by charging condenser I connectedacross the actuating coil in series relation through device I I and bythe discharge of the capacitance I0 through the actuating coil. Moreparticularly, relay 9 is adapted to operate simultaneously with relay 1upon closure of key 8. Reactors and I2 are short-circuited by relay 1 solong as its contacts 5 are closed. Contacts I 3 of relay 9 remain openso long as the interval of time between successive operations of key 8do not exceed a predetermined Value. However, if this time interval doesexceed this value the discharge current of condenser IIl through theactuating coil of relay 8 decays to a value which die-energizes therelay closing its contacts I3 thereby short-circuiting reactor I2independently of the operation of relay I. In this manner by virtue ofthe reduction in the value of the serially connected impedance, thecurrent transmitted to the lamp I is increased to a value greater thanthe simmering current but less than the current transmitted theretoduring high level operation.

Concerning the operation of the system, upon energization of the supplycircuit heating current will be supplied to the electrodes 2 of lamp I,and the value of this heating current remains substantially constantwith constant supply circuit voltage. Due to the presence of thereactors 4, 5 and I2 a predetermined value of simmering current issupplied to lamp I.

When the system is used as a signalling system, for example in thetransmission of code, key 8 will, of course, be depressed intermittentlyfor difierent periods of time with different intervals betweensucceeding periods of operation. When key 8 is depressed, relay 1operates imme diately, and its contacts 6 are closed therebyshort-circuiting reactors 5 and I2. Relay s also operates immediatelyand simultaneously with relay 1, being energized by rectified currentfrom the supply circuit through device II. The opening of contacts I3 ofrelay 9 thus prepares for the connection of reactor I2 in series withthe lamp when relay 1 is de-energized in the opening of key 8 if thedelay between times of operation becomes excessive. Due to the fact thatrelay "i short-circuits reactors 5 and I2, a much larger current istransmitted to lamp i. Condenser Iil becomes charged and by virtue ofthe discharge path thereacross and the incident flowing current throughthe actuating coil, the relay 9 is 4 held closed so long as the key 8 ispressed periodically providing that the interval between successiveclosures is not too large. If the key 3 is released for a short periodof time, for example, greater than the length of time between words in amessage, condenser [0 becomes discharged and the rela 9 is de-energizedallowing the contact I3 to close and causing the reactor I2 to becomeshort-circuited. Therefore, the simmering power supplied to the lamp isautomatically increased as compared to the simmering power betweenrapidly occuring flashes. By thus increasing the simmering value of thecurrent during periods between signalling flashes it is ensured that thelamp is ready for immediate operation, while at the same time the ratioof the luminous output of the lamp during flashes to that during theintervals between flashes is increased.

If the above described system is to be operated on direct current, thenof course the impedances may be resistances, but the electrical circuitaffording the time delay feature will operate on either alternating ordirect current. It is within the purview of my invention that othertypes of time delay circuits such as thermionic grid controlled electricvalves now well known in the art may be used in place of theelectro-responsive device or relay 9 and the associated condenser.Furthermore, it will be appreciated that, if desired, the relay 9 may beof the relatively small control type and an intermediate power contactormay be used between relay 9 and the impedance to be controlled thereby.

In one system constructed in accordance with my invention the powersupplied to the discharge lamp was 10,000 watts, and the simmering powerwhen the lamp was not signalling was 500 watts. The simmering powerduring signalling is 300 watts. Under such conditions the ratio offlashing to simmering wattage has been increased from 20:1 to 33:1, andthe steady light from the lamp has been reduced to approximately 1000candlepower, while the flash is approximately 55,000 candlepower.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A method of producing intermittent flashes of light by utilizing anelectric discharge lamp energized from a source of current through animpedance, which method comprises intermittently short-circuiting theimpedance to increase the power input to the lamp, maintaining the arcdischarge in the lamp during periods of reduced power input, andcontrolling said impedance to increase the value 'of the currenttransmitted to the lamp to a value greater than that existing duringperiods of reduced power input and less than that existing duringperiods of increased power input, when the period of reduced power inputis in excess of a predetermined time.

2. In a system for producing intermittent flashes of light by utilizingan electric discharge lamp, the combination comprising a source ofcurrent, an impedance connected in series relation with said source andsaid lamp, initiating means susceptible of intermittent operation, meansresponsive to said initiating means for intermittently short-circuitingsaid impedance, a second impedance in series with the first-mentionedimpedance, at time delay means responsive to said initiating means forcontrolling said second impedance to increase thepower input to the lampto a value in excess of the reduced power input value and less than thatexisting during periods of increased power input.

5 3. A method for producing intermittent flashes between succeedingintermittent flashes exceeds of light by utilizing an electric dischargelamp, a predetermined value. which method comprises short-circuitinginter- HARRY KEBBELL BOURNE. mittentiy an impedance in series with thelamp, maintaining an arc discharge through the lamp 5 REFERENCES CITED drin p ds f reduced power input y hea The following references are ofrecord in the ing electrodes thereof, and short-circuiting a file ofthis patent;

part of said impedance to increase the power input UNI to the lamp to avalue in excess of the reduced v TED STATES PATENTS power input and.less than that existing during 10 Number Name Date periods of increasedpower input when the time 2,178,423 Inman 1939

